We have made great strides to reach the modern era of antiretroviral therapy (ART) in resource wealthy settings. We now know that optimal clinical outcomes require maximal suppression of viral replication by combination ART to maintain the integrity of the immune system and to avoid the selection of drug resistant HIV. We also know that drug resistance (DR) represents a real public health threat since it can be spread to others thereby limiting the usefulness of certain ART regimens to them. Our current standard clinical practices in resource wealthy settings include starting combination ART when clinically appropriate, regular clinical, viral load and CD4+ count monitoring, and DR testing when viral replication is detected in the setting of ART exposure to inform the selection of appropriate second and third line ART regimens. This same standard of HIV care is not currently available in many resource limited settings. In many regions, struggles continue to provide access to combination ART and CD4 count monitoring where most of the people infected with HIV live. In these settings, the availability of viral load monitoring and DR testing for all practical purposes remains unattainable for the vast majority of patients, related to the lack of infrastructure and technical expertise in many instances. Even when infrastructure and expertise exist, cost often prohibits their use. We feel that it is imperative and urgent to overcome the obstacles to provide optimal HIV care, including virologic monitoring and DR testing, for patients receiving ART in resource limited settings. This will not only improve the standard of care for individual patients but also reduce the transmission of HIV DR. In the absence of viral load monitoring and DR testing a secondary epidemic of drug resistant HIV may proceed unchecked with disastrous public health consequences. To this end, we propose a method that may overcome some of these obstacles and ultimately bring virologic monitoring and DR testing to resource limited settings in a potentially cost effective and sustainable manner. In this study, we will compare the 'gold standards' of (i) individual viral load testing and drug resistance genotyping for samples found to virologic failure to (ii) an assay that combines nucleic acid testing and DR genotyping (NAT+DR assay). This NAT+DR assay combines dilution techniques via sample pooling, PCR amplification of the HIV-1 reverse transcriptase (RT), deconvolution algorithms to identify patients with virologic failure, and sequencing of PCR product to determine drug resistance. To evaluate this method, we will enroll 500 HIV-infected patients followed at YRG CARE on first-line ART and screen baseline and six month samples with both individual viral loads and the new NAT+DR assay. We will then evaluate the NAT+DR assay based on accuracy, efficacy, turnaround time of results and costs. We have proposed a quick start and aggressive timeline for this project because we feel that the rapid validation of these methods could be crucial for the health of many living with HIV in the world.